Shape-memory alloys have found a wide variety of uses in recent years. Such alloys have two primary states which are described in the prior art as the martensitic state and the austenitic state. In the martensitic state the alloy is weaker and malleable to a predeterminable extent. In the austenitic (or memory) state the alloy is stronger or more rigidly resilient. The alloy may be readily deformed under the martensitic state but then recovers from such deformation to its initial shape upon heating above the transformation temperature to recover such deformation to its austenitic state. The temperature condition under which such states occur is predeterminable in accordance with the alloy content of the metal. The two crystalline states of the alloy are above or below a transformation temperature lying within a critical temperature range. The transformation temperature is generally determined by the percentage of the constituent components (usually nickel and titanium) of the shape-memory alloy.
The alternate states of such alloy, the relatively sharp temperature transformations between these states, and the almost limitless ability of the alloy to reverse the states, have found many novel uses. It has been proposed heretofore to use shape-memory alloy in parts or devices wherein the alloy's relatively weaker malleable state absorbs displacement or deformation forces without permanent damage to the rest of the structure or device. After undergoing such deformation the article or structure may be restored to its original form or configuration by heating the part just above the transformation temperature. For example, eyeglass frames including temple and nose pieces, as disclosed in copending and commonly owned U.S. application Ser. No. 876,077, filed June 19, 1986, the disclosure of which is incorporated herein by reference, may be constructed using such shape-memory alloy as at least the reinforcing members for such frames. Such spectacles are not only more comfortable to wear, but also are immediately restorable to their original form merely by immersion in hot water, say 120.degree. F., if dropped or inadvertently deformed during wear.
However, in prior known devices, the shape of the device in the austenitic state of the shape-memory alloy corresponds to a desired shape when the device is built and heretofore has required replacement or remanufacture to give the article a different shape in its austenitic state. The alloy is highly resistant to mechanical reshaping after it passes from the martensitic to the austenitic state. The method of the present invention is directed to reshaping articles, or portions of articles, quickly and easily without such mechanical reworking of the article to produce a new austenitic state. Accordingly, eyeglass frames or other personal wear items, such as shoes, orthodontic braces, partial dental plates or inner or outer clothing that require reinforcing elements such as bra underwires and corset stays may be readily conformed to the wearers individual anatomy or fashion at or near the point of use. The method is also particularly useful in shaping or reshaping hand-held tools, or other implements, such as surgical clamps, scalpels and the like to the user's desire or need.